Outdoor Unit; Refrigerant Pipe Selection; Copper Pipes, Sizes, Connection And Insulation - Hitachi FSXN Series Service Manual

3 Piping work and
refrigerant charge

3.1 Outdoor unit

3.1.1 Refrigerant pipe selection

The RAS-(8-54)FSXN outdoor units can work as a heat pump system, by means of a two-pipe system (gas pipe and liquid
pipe), or they can work as a heat recovery system by means of a three-pipe system (high and low pressure pipes and liquid
pipe), requiring in addition the CH units supplied as accessories.
There is an optional specific pipe connection kit available according to the power of the outdoor unit:
Operating mode Outdoor unit
RAS-(20-24)FSXN
Heat pump system RAS-(26-36)FSXN
RAS-(38-54)FSXN
RAS-(20-24)FSXN
Heat recovery
RAS-(26-36)FSXN
system
RAS-(38-54)FSXN
¿ Pipe size selection
Select the pipe size in line with the following instructions:
1 Between the outdoor unit and the branch pipe (multikit): select the same pipe connection size as for the outdoor unit.
2 Between the branch pipe (multikit) and the indoor unit: select the same pipe connection size as for the indoor unit.
C A U T I O N
• Do not use refrigerant pipe sizes other than those indicated in this manual. The diameter of the refrigerant pipes
depends directly on the power of the outdoor unit.
• If larger diameter refrigerant pipes are used, the circuit lubrication oil tends to separate from the gas carrying
it. The compressor will be seriously damaged due to a lack of lubrication.
• If smaller diameter refrigerant pipes are used, the gas or liquid refrigerant will have serious difficulties in
circulating. System performance will be affected. The compressor will run under more severe conditions than
foreseen and will be damaged in a short space of time.
¿
Multi-kit or distributor selection
N O T E
• Pipe connection sizes on outdoor units, indoor units and the multi-kit or distributor vary depending on the
system. Consult the Technical Manual for the SET FREE Series FSXN.
• The sizes of the indoor and outdoor units are different. Adjust the flare adapter (accessory) to the indoor pipe
connection.

3.1.2 Copper pipes, sizes, connection and insulation

¿ Copper pipes and sizes
C A U T I O N
• The copper pipe used in the refrigeration installations is different to the copper pipe used in installations
carrying domestic or heating water.
• The copper pipe for refrigeration installations is especially treated for outdoors and indoors. The interior
surface finish makes it easier for the refrigerant to circulate and withstands the action of the lubricant oil applied
to outdoor equipment.
Prepare the copper pipes provided by the supplier.
30
SMGB0065 rev. 1 - 12/2010
No. of units Connection kit
2 MC-20AN
2 MC-21AN
3 MC-30AN
2 MC-20XN
2 MC-21XN
3 MC-30XN
Indications:
• Gas pipe: 1 set.
• Liquid pipe: 1 set.
• Gas pipe, high pressure: 1 set.
• Gas pipe, low pressure: 1 set.
• Liquid pipe: 1 set.